In a general communication system, each of user equipment (UE) and an enhanced Node B has a protocol stack including a plurality of layers. The plurality of layers includes a Packet Data Control Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer, and a physical layer (hereinafter, referred to as ‘L1’).
The L1 is a layer for providing an information transfer service using a radio transfer technology, and transport channels are connected between the L1 layer and the MAC layer. The transport channels are defined by such a manner that a certain data is processed in the physical layer. The physical layer encodes data by means of a scrambling code assigned to each cell and a channelization code assigned to each physical channel, so that the encoded data may be transmitted wirelessly.
The MAC layer and the RLC layer are connected through a logical channel. The MAC layer transfers data, which the RLC layer transfers through a logical channel, to a physical layer through an appropriate transfer channel, and transfers data, which the physical layer transfers through a transfer channel, to the RLC layer through appropriate logical channels. Further, the MAC layer inserts additional information into the data transferred through the logical channels or the transfer channels, or analyzes the additional information inserted in the data and then performs a suitable operation, so as to control a random access operation.
The RLC layer takes charge of setting and releasing logical channels, and performs a function of dividing or connecting a service data unit received from a superordinate layer into appropriate sizes and a function of correcting an error. The PDCP layer is arranged at a superordinate layer of the RLC layer so as to perform a function of compressing and restoring a header of data transmitted in the form of an Internet Protocol (IP) and a function of transmitting data without a loss in a state that a Radio Network Controller (RNC) providing a service to a certain terminal with a mobility is changed.
In a general adaptive streaming scheme, there is no exchange of information between the MAC layer and the RLC layer of an enhanced node B performing the above-mentioned function. Therefore, the conventional enhanced node B estimates a bandwidth for a service provided to the UE through feedback information received from the UE, and provides the UE with a service, i.e., a video, with a quality corresponding to the estimated bandwidth. As an example, in the case that the enhanced node B provides the UE with a video streaming service, it is assumed that a bandwidth which the UE can use is about 100 kbps. In this case, the enhance node B streams a video of an image quality with a bandwidth of about 100 kbps to the UE. However, as the UE moves in a radio environment, a case that an available bandwidth is reduced by 10 kbps may occur. In this case, since there is no exchange of the information between the MAC layer and the RLC layer of the enhanced node B, the RLC layer cannot detect a change of the available bandwidth of the UE. Thus, the video of the image quality with a bandwidth corresponding to the changed bandwidth cannot be transmitted to the UE.
Further, since the enhanced node B and a conventional server, which is an external host transmitting and receiving a packet data, cannot identify a bandwidth which a corresponding UE can use, a Transmission Control Protocol (TCP) layer transmits a packet corresponding to a predetermined window size to the UE while gradually increasing the window size for a transmission. Accordingly, as the size of the TCP window gradually increases, it takes a certain time to reach an appropriate TCP throughput.